At present, the marking systems For cork stoppers used in the natural cork stoppers processing industry are based on offset ink printing systems, or marking systems with hot metal marking plates warmed with electrical heaters or by induction.
Also, in the case of natural cork stoppers substitutes, using synthetic materials such as polypropylene, thermoplastic foam or silicone, the process of marking is done by offset printing, tampography, thermal transfer, using special inks and drying methods to help fixing the ink to these materials, with great difficulty due to non-absorption of the material.
In the state of the art, it is known and widely extended in the cork stoppers processing industry the utilization of marking systems usually rotating cork stoppers by contact, such as those described in the invention patents GB164505A, GB187588, US2003/0127000A1, WO01/08893A1, WO95/13883A1, WO2004/080813A2, US2003/0118745 where the process of marking stoppers is generally done by techniques of: 1) temperature and pressure applied on the body of the stopper through a hot metal stamp or plate, maintained at high temperatures and generated through electrical heaters or induction of high-power in contact with the marking plate, which it has previously been mechanized to have a relief according to the shape of the logo or image that the winery wants to see transferred into the body of the stopper, and that due to the temperature and pressure applied on the body of the stopper will result in a mark based on the color change of the affected area of the cork due to the effect of “roasting” darker and/or deep depending on temperature and/or pressure applied; 2) ink of one color; 3) several inks.
Nowadays the stamp plate must be made to place it into the marking stoppers machine. The manufacture of this stamp (silicone or metal, depending on the marking: by ink or by temperature and pressure) it is outsourced to specialized mechanical companies.
Another drawback of the cork marking process using stamps, is that the cork stopper processing company is forced to store each one of the marking plate sets, requiring large storage space in the production facilities as the years go by.
It is also true that these marking plates require maintenance, repair and replacement in many cases for other new marking plates, because by using them they become completely or partially damaged.
The process of body marking of cork stoppers with ink (heads or flat sides are marked with hot metal plates) requires a 24 hours drying process in order to ensure the ink is well fixed on the stoppers surface.
Each phase of the stopper manufacturing process, especially those that require the application of products for its treatment, it is usually made in batches between 5,000 and 20,000 stoppers in the same machine to which chemicals are added in the appropriate quantities and proportions. At present and at the end of the process, stoppers do not usually incorporate any information related to these batches called “washing batches.” Therefore, if the winery finds, within the entire order, a sole stopper without the appropriate chemical treatment (as an example—too much paraffin, poor color matching, etc.), the winery for security tends to return the whole order to the cork processing company, which can involve batches up to 100,000 with the inconvenience that this may represent.
Today, for process traceability reasons, it is increasingly required to divide the stoppers into lots to take control. This division included on the marking pattern represents a big problem for the current systems, since it involves an ongoing marking plate change or changing some parts of the marking plate, as if it was a numbering revolver that changes numbers. Usually this process is manual and limited to a few numbers/letters and requires stopping the marking process to clean and substitute the marking plates with the numbers to change.
Once everything is ready, the ink marking process takes place as follows: the marking plate is to absorb ink to mark the stoppers. This process is done continuously, where one stopper after another are rolled at high speeds and forced to pass under a tangential rotating wheel that contains the marking plate attached around this rotating wheel which has previously been impregnated with a particular amount of ink, transferring the ink that a roller had previously deposited in the relief of the marking plate.
On the other side, even though this ink marking method since its introduction years ago reached a greater image resolution for wineries in their marking on the stoppers, bringing to these marking patterns drawings of castles, profiles of the winery and its landscape, grounds flowers, etc., compared with the markings of the stoppers obtained previously with the old hot marking plates/metal stamps previously used for marking by heat and pressure, it is noteworthy that the process still includes serious and annoying inconveniences associated with the ink marking, and especially in low-porous materials such as cork and that the cork industry needs to improve.
Some of the drawbacks associated with ink marking stoppers are: 1) The difficulty in performing marking patterns whose images/logos have large areas that should be marked, resulting in a cluttered image by excess of ink; 2) the need to let the cork stoppers dry for about 24 hours after being marked with ink, prior to the next silicone/paraffin process described; 3) using a specific ink for application in materials for the food industry, that it is being used to only mark the body of the stopper, not being allowed by the health authorities the use on the ends because sooner or later one of the ends will be in contact with the beverage contained inside the bottle in question; 4) when changing a marking plate/stamp it is required to stop the machine between 5 and 10 minutes not only to replace the marking plate, but also clean up the marking mechanism and avoid the accumulation of waste that would hinder the process and deteriorate the marking quality (it has been measured the machine's stop average time for cleaning and changing marks made by a qualified operator who oversees two ink markers, in about 1 hour a day per shift); and 5) the use of inks in food products that governments' of all countries and end users in general to eliminate to avoid risks of food contamination consumers.
Although such systems work quite well, they require high maintenance, have consumables and marking plates costs, and require high labor for such tasks as well as monitoring which represents a clear disadvantage for the industry.
On the other hand, published patent application WO2004/007599 discusses the preparation of a type of synthetic stopper formed by mixing thermoplastic foamed material with special additives for the reaction to laser radiation, as well as the specific method for marking these stoppers. To point out that the patent refers to the method of marking synthetic stoppers of that composition, that should be previously made with the right mix including the special additive, in addition to a specific type of laser for its marking, and an optical setup and focalization that are critical to achieving a proper result that does not mar the surface of the stopper, resulting in a low reliability marking process, low speed and the inability to mark the whole body of the stopper as well as their heads, a high investment and a variable cost (additive).
Despite the existence of various laser techniques, already combined in other previous patents and for other applications, neither they are presented in this invention's configuration, nor are able to generate the benefits described in the following paragraphs, much less in the processing of materials with cylindrical geometry and rotational movement at high speed such the case of the cork stoppers.
Moreover, in the past, certain technological barriers have created a bias against the use of lasers to form high-speed graphics in cork stoppers or cylindrical surfaces rotating at high speed, primarily due to two reasons: 1) High frequency repetition rate pulse generation, with variable duty cycle and frequency, pulse to pulse, especially with infrared laser types (FIR); and 2) means of spatial modulation able to generate modulation frequencies up to 800-1000 Hz and mechanical amplitude angles up to +/−30 degrees.
In the market there are different types of laser generators according to the generated wavelength and power, which include the infrared radiation generation (CO2, Nd: YAG, Nd: YVO4, . . . ) with the CO2 being the most appropriate for the application described below due to the significant absorption of the described material (natural cork). There is, however, an existing a serious problem that impedes the direct use in this application of any of the above mentioned, mainly because none of them is capable of generating frequency pulses above 100 kHz. (This application may require repetition frequencies above 500 kHz.) with duty cycle and frequency variable from pulse to pulse, and constant power level along each pulse length.
At the time that these settings were tried, the result was that the laser was not able to produce a regular marking, either was making holes, burning in-depth, or melting the material in the contact point with the laser beam, generating defects in the material to be processed, or that the maximum acceptable speed for the process was so slow that it was necessary to rule out the technique for not being able to be industrialized and require high investment.
In the event that such technological barriers would disappear, a laser system would be a desirable method to generate logos and high definition images on stoppers and cylindrical materials, while allowing an electronic control with all the added benefits due to the latter, such as the generation of variable codes to, as an example, insert traceability information of the material to process, batches, dates, sequential numbers, and alphanumeric codes defined by the user, even mixed with images and logos that up to date are being marked on the surface of these materials, electronic storage designs reducing the space needed, etc.
The main purpose is the marking process speed to ensure the productivity expected by the market, in line with the existing cork handling equipment. This object not only directly affects to the type of laser and the spatial and temporal modulation systems to use, which should have benefits far superior to those available so far on the market, but also how these elements are managed to get the most of those resources.
Another object of this invention focuses on how the cork stopper travels in the handling process as well as how to ensure the entire perimeter of the body is being displayed, in order to be able to mark it completely. This defines the ergonomics of the application and programming software that controls and synchronizes the entire process.
At present, there does not exist any laser marking system that uses the technology described below, representing the invention of a method and systems with an improved technology compared with current systems.